1. Field
The present disclosure relates generally to communications, and more specifically, to a frequency agile transceiver for use in a multi-band handheld communications device.
2. Background
The demand for wireless communications has led to the development of an ever increasing number of wireless services. Wireless services started with a blueprint that relied on cellular technology. Cellular technology is based on a topology in which the geographic coverage region is broken up into cells. Within each of these cells is a fixed radio transmitter and control equipment to communicate with mobile users. Cellular services, which operate between 824-894 MHz in the United States, originally used analog signals to support wireless communications. Today, various upgrades have been made to the cellular system to incorporate digital technology.
PCS (Personal Communications Services) followed years later. PCS is a digitally based communications system which uses a broadband operating frequency between 1850-1990 MHz to support voice, data and video applications. More recently, IMT (International Mobile Telecommunications) has been deployed to provide a framework for worldwide access by linking terrestrial and/or satellite networks. IMT has an operating band between 1920-2170 MHz. Thus, one can readily see that a mobile user will need a multi-band wireless communications device to access both cellular and PCS services. To make matters worse, frequency allocations for cellular and PCS, as well as other wireless services, are different throughout the world.
One of the advantages of a multi-band handheld wireless communications device is that it can be shipped anywhere in the world, reducing mass production volume costs and avoiding the need for differentiated product lines for devices going to different locations. Consumers may also appreciate a multi-band handheld wireless communications device to avoid purchasing multiple devices.
In current implementations of multi-band handheld wireless communication devices, a separate channel is provided for each wireless service. Each channel includes appropriate transmit and receive filters coupled to a duplexer. An RF switch may be used to connect the duplexer in the selected channel to the antenna. As the number of desired bands increases, the cost and complexity of realizing a multi-band handheld wireless communications device becomes prohibitive. The additional losses that arise from using an RF switch adversely impact system performance. Accordingly, there is a need in the art for an improved multi-band handheld wireless communications device.